The insulated gate bipolar transistor (IGBT) generally is a common power switching device controlled by a voltage. It has the features of a large input capacitance, a high input resistance, high voltage resistance, a high work temperature, a simple control circuit and the like, and becomes a main device of the power electronics apparatus at the present stage. The reverse conducting insulated gate bipolar transistor is a new IGBT device, and it integrates an IGBT structure and a reverse conducting diode structure on a same chip, which can improve the passage of non-balanced carriers and optimizing the tail current. The reverse conducting IGBT device has many advantages of a small size, a high power density, a low cost, a high reliability and the like.
The method of manufacturing the reverse conducting diode structure at the back side of the device in the method of manufacturing the common reverse conducting IGBT has two main manners. A method of manufacturing the reverse conducting diode structure of the reverse conducting IGBT is implemented by using two back side photoetching processes. Particularly, a P+ type area is formed by firstly performing selective implantation and diffusion processes, and then an N+ type area is formed by performing selective implantation and diffusion processes again. As a result, the N+ and P+ areas can be formed at intervals on the back side of the reverse conducting IGBT. The interval N+ and P+ areas are the reverse conducting diode structure. The back side N+ area of the reverse conducting IGBT formed by using this manufacturing method is shallower, and has a higher requirement for controlling the process. Once the doping concentration of the N+ area becomes higher, when the formed reverse conducting IGBT is forward conducted, a large implantation effect can be formed, resulting in losing the function of the reverse conducting IGBT.
Another method of manufacturing the reverse conducting diode structure of the reverse conducting IGBT is described as follows. After the front side process is performed and the back side P+ layer is formed, digging of the trench is performed, and then the reverse conducting diode structure of the reverse conducting IGBT is finally formed by filling back side metal in the trench. The method of manufacturing the reverse conducting diode structure of the reverse conducting IGBT mainly use the means of digging of the trench and filling of the back side metal to form he reverse conducting diode structure. However, because the metal in the trench at the back side of the reverse conducting IGBT is limited by requirement of collector metal of the reverse conducting IGBT, the parameters of the reverse conducting diode can be adjusted only by adjusting the width and depth of the dug trench, resulting in troubling of the adjusting process and a high requirement of controlling the process. Therefore, from the above process methods, it can be understood that the common method of manufacturing the reverse conducting diode structure at the back side of the reverse conducting IGBT device has a higher requirement of controlling the manufacturing process, and a larger difficulty of manufacturing.